The influence of the stem effect in Eu-doped silica optical fibres

The depth-dose-profile and the transversal beam profile of a 6 MV photon beam are measured by means of Eu-doped silica optical fibres. In both cases, a non-negligible influence of the stem effect was observed as consequence of the change in the relative contribution of the Cerenkov light while varying the vertical and lateral position of the fibre. The approach for removing the spurious luminescence signal based on the radioluminescence (RL) spectral analysis proved to be effective and independent of the irradiation configurations.